Energy-efficient home basics. U.S Department of Energy

Contributed by Adrian Martin

There are a lot of different reasons to build green. You might want to reduce your impact on climate change. You might want to decrease your monthly energy bill. Or you might see green renovation as profitable. After all, some homebuyers explicitly look for green properties.

Depending on where you live, you might receive all kinds of subsidies for green building and renovation. Whether you’re building a new home or renovating your current home, you can aim at a variety of different standards and metrics.

The two we’re going to look at today are Net Zero and Passive House. They have similar goals: to decrease energy use in the home. To start, let’s break down what we mean by each term.

Net Zero and Passive House defined

Net Zero homes are the easiest to explain: they have an annual net carbon emission of zero or less. Homes can achieve negative carbon emissions by providing electrical grids with more renewable energy than they consume. They can do so through power generating devices like solar panels, home wind turbines, and other home renewable systems.

Passive House, conversely, is a strict set of standards set in place by the Passive House Institute.  The Passive House standards do not include net-zero energy consumption. Rather, they focus on reducing energy usage through a variety of means–– primarily through insulation.

Total energy use in the home must not exceed 60 kWh per square meter per year, and the home must have an airtightness of 0.6 or less. In addition, no more than 15 kWh per square meter per year can be used for heating and cooling. (Editor’s note: for a fuller explanation, see Saving Energy with Passive Building on this site.)

Some people say that Net Zero homes are the path forward. Others say that Passive House is the way of the future. The reality is that neither group is wrong. In fact, they’ll get along quite nicely.

Net Zero homes don’t need to be Passive Houses. You could, for example, have a gigantic solar array in your yard that nets way more renewable energy than you need and far exceeds your home’s carbon consumption. It would technically be Net Zero, but if it was uninsulated and used fossil fuel heat, it would still not be green.

Similarly, the Passive House standard is not carbon neutral; it’s just energy efficient. If we converted all homes on the planet to the Passive House standard, we’d see a substantial reduction in our collective carbon footprint, but we’d still emit greenhouse gas.

The Net Zero Passive House

Passive House contribution

Public domain from Wikimedia Commons

The solution, then, is to merge these two concepts together. Using Passive House innovations and coupling them with renewable energy sources, we can create a Net Zero Passive House. Let’s take a look at what that would entail:

Heating and cooling account for the majority of your home energy costs. The innovation of Passive House is reducing the amount of heating and cooling you need by focusing on the building envelope. Your building’s envelope is, in essence, what keeps the indoor climate separate from the outdoor climate.

By focusing on insulating every inch of your home, you create a building envelope that keeps you cool in the summer and warm in the winter. That’s because heat transfer works both ways. Heat will leave your home in the wintertime and enter your home in the summer if you don’t have enough insulation.

That means you’ll need to use high-quality, dense insulants in your walls, floors, and ceiling. You’ll also need insulating windows and doors. All of this insulation comes with a problem, though; it restricts airflow. When adhering to the Passive House standard, you need to pay attention to your home air quality. Stale air is bad for your health.

The solution is found in devices known as Heat Recovery Ventilators (HRVs) and Energy Recovery Ventilators (ERVs). These devices exchange fresh air from outside for the stale air within. HRVs transfer the heat from your stale air to warm the cooler, outdoor air. Or they cool air in your home with heat transfer in the opposite direction.ERVs work on the same principle but they transfer humidity as well, keeping your home’s moisture level even.

Net Zero contribution

The Net Zero side of things, focuses on technologies that allow you to reduce energy consumption while generating energy yourself. They might use geothermal heat pumps instead of traditional gas furnaces and electric air conditioners to heat and cool your home. These heat pumps draw thermal energy from the ground; in many climates where this would otherwise not be sufficient, Passive House insulation allows for their use.

You can substantially reduce the amount of energy you’ll need to generate yourself to reach Net Zero when your home is already designed to limit energy consumption.

That said, there are still a number of potential advantages to installing arrays that produce more energy than you consume. Check in your region to see if your utility allows for net metering – where you sell energy back to the grid. Depending on your utility, you may be able to get credits towards your power consumption in higher demand months (like winter). You may even be paid in cash for the energy you provide to the grid!

For most homes, using solar panels is the easiest way of producing your own energy. Those with a lot of land might opt for wind power; land with streams might even benefit from micro or pico hydropower.

By coupling together Passive House and Net Zero metrics, we can manage to create the true home of the future: one with low energy consumption and high renewable energy production. Imagine a universe in which every house produces more energy than it consumes; we’d be in an energy paradise. Fortunately, as technologies become more affordable and techniques are refined, we’re sprinting towards that future.

Adrian Martin is a writer based in Canada. She writes articles with a focus on marketing and home improvement for a variety of businesses. She has been engaged in writing how-to guides and informative articles.